Vibration welding has established itself for the welding of plastic parts. In this procedure, the plastic parts to be welded are rubbed against each other at certain contact surfaces. Through this friction, the melting temperature of the plastic of the parts to be connected is reached in the joint zone so that the plastic is plasticized and connected at the contact surfaces.
For vibration welding, individual oscillating heads are generally operated in vibration welding machines. This technology is suitable for welding different sizes of plastic parts, such as vehicle dashboards. Different sized machines are used depending on the size of the plastic parts. They are differentiated based on tool weights, surfaces to be welded and installation size.
In order to be able to connect larger plastic parts, it is economical and makes more sense technically to increase the number of oscillating heads in the vibration welding machines rather than continue to increase the size of the individual oscillating heads. Thus, larger constructions are feasible through the series connection of the electrical components, such as electrical coils, and the mechanical coupling of the mechanical components. The mechanical coupling is of central importance in particular for the larger constructions, since only in this manner can a frequency- and phase-equal oscillation of the connected mechanical components and oscillating heads be achieved. However, it is an important disadvantage that, up to now, for construction reasons, only two oscillating heads have been able to be connected with each other and thereby synchronized. However, if a plurality of oscillating heads is required for the vibration welding of large plastic parts, modulation difficulties of the oscillating heads amongst themselves result. For example, an unreliable connection of the plastic parts is created through an uncontrolled, non-in-phase oscillation of the oscillating heads within the vibration welding machine.
It is thus the object of the present invention to provide an apparatus and a method for vibration welding, with which a reliable connection of the plastic parts can be ensured even when using a plurality of oscillating heads or oscillating systems, because the sum of the oscillating systems or oscillating heads works just like a large oscillating head.